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موجز عن البحث:
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Abstract
BACKGROUND:
Although
antiseptics are some of the most widely used antibacterials in hospitals,
there is very little information on reduced susceptibility to these biocides
and its relationship with resistance to antibiotics.
AIM:
To
determine the relationship between reduced susceptibility to biocides and the
carriage of antiseptic resistance genes, cepA, qacΔE and qacE, as well as
identifying the role of efflux pumps in conferring reduced susceptibility.
METHODS:
Susceptibility
was assessed for five biocides: chlorhexidine, benzalkonium chloride,
Trigene, MediHex-4, Mediscrub; and for 11 antibiotics against 64 isolates of
Klebsiella pneumoniae. Susceptibility to all compounds was tested by the agar
double dilution method (DDM) and the effect of efflux pumps on biocides
determined by repeating the susceptibility studies in the presence of the
efflux pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The
presence of the cepA, qacΔE and qacE genes was identified by polymerase chain
reaction.
FINDINGS:
The
bacteria were not widely antibiotic resistant though a few showed reduced
susceptibility to cefoxitin, chloramphenicol and rifampicin and
later-generation cephalosporins but not to carbapenems. Biocide
susceptibility, tested by DDM, showed that 50, 49 and 53 strains had reduced
susceptibility to chlorhexidine, Trigene and benzalkonium chloride,
respectively. The antiseptic resistance genes cepA, qacΔE and qacE were found
in 56, 34 and one isolates respectively and their effects as efflux pumps
were determined by CCCP (10 mg/L), which decreased the minimum inhibitory concentrations
(MICs) of chlorhexidine and Medihex-4 by 2-128-fold but had no impact on the
MICs of benzalkonium chloride, Trigene and Mediscrub.
CONCLUSION:
There
was a close link between carriage of efflux pump genes, cepA, qacΔE and qacE
genes and reduced biocide susceptibility, but not antibiotic resistance, in
K. pneumoniae clinical isolates.
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موجز عن البحث:
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Abstract
Six
isolates of Klebsiella pneumoniae were obtained from the Royal Infirmary
Edinburgh (RIE), Antimicrobial susceptibility was tested by the agar double
dilution method (DDM) and disk diffusion methods following the British
Society for Antimicrobial Chemotherapy guidelines showed reduced susceptibility
to cefotixin, chloramphenicol and rifampicin but not to third-generation
cephalosporins and carbapenems. The sensitivity of these strains was tested
against five biocide preparations; Chlorhexidine, Benzalkonium chloride,
Trigene, MediHex-4 and Mediscrub. When measured against the minimum
inhibitory concentration (MIC) of the active component, the strains were
resistant to Benzalkonium chloride and Trigene but sensitive to Mediscrub.
Most strains showed decreased Susceptibility to CHX and this correlated to
the carriage of the cepA gene encoding efflux. There was no correlation of
susceptibility with the carriage of the qacΔE efflux gene nor an association
with antibiotic resistance.
The
minimum bactericidal concentration (MBC) of the active component of each
biocide was determined. The high MBCs of Mediscrub and Trigene, more than
500-fold the MIC indicates that these compounds are mainly bacteriostatic and
are not effective in eradicating Klebsiella pneumoniae. On the other hand,
the MBCs of Chlorhexidine and MediHex-4, which contains chlorhexidine, were
lower and less than 10-times the MIC value indicating they are effective in
killing the organism. However, killing capability of chlorhexidine is
susceptible to the presence of organic matter and this could compromise this
effect.
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